Jennifer A. Defant, M.S., C.G.C. Certified Genetic Counselor Division of Genetics and Metabolism University of Florida

Size: px

Start display at page:

Download "Jennifer A. Defant, M.S., C.G.C. Certified Genetic Counselor Division of Genetics and Metabolism University of Florida"

Brittany Magdalene Price
8 years ago
Views:

1 Jennifer A. Defant, M.S., C.G.C. Certified Genetic Counselor Division of Genetics and Metabolism University of Florida

2 60% of childhood hearing loss is genetic Syndromic Nonsyndromic 40% of childhood hearing loss is caused by infectious/environmental factors prenatal infections (CMV, toxoplasmosis,etc) meningitis low birth weight/prematurity Oto-toxic medications mechanical ventilation trauma

factors prenatal infections (CMV, toxoplasmosis,etc) meningitis low

4 Nonsyndromic hearing loss Categorized by mode of inheritance: DFN- X-linked deafness (~1%) DFNA - Autosomal dominant deafness (12%) DFNB - Autosomal recessive deafness (56%) Mitochondrially inherited deafness (~1%) Syndromic hearing loss 300+ syndromes with deafness as component

- Autosomal recessive deafness (56%) Mitochondrially inherited

5 Chromosomes in every cell 23 pairs of chromosomes for total of 46 One from each pair we inherit from mom and the other from dad Chromosomes contain our genes

6 Modes of inheritance for non-syndromic hearing loss Autosomal Dominant DFNA 12% Autosomal Recessive DFNB 56% X-linked DFN 1% Mitochondrial 1%

7 Why is genetic deafness so common? There are so many genes associated with hearing loss

8 Complete family history, prenatal and medical history, developmental assessment and physical examination Associated testing may include: EKG, audiologic and vestibular testing, ophthalmology exam, X rays, CT/MRI of inner ear

Associated testing may include: EKG, audiologic and

9 Account for 20-30% of genetic HL >300 syndromes Each syndrome is relatively rare Syndromes identified by: Physical examination findings Internal ear malformations Physiological traits (e.g., ECG changes)

10 Anatomy Review Vestibular canals Dural surface Endolymphatic sac and contiguous membrane Vestibular aqueduct Perilymphatic aqueduct Ear drum Cochlea Stapes Middle ear cavity Perilymphatic fluid

Vestibular aqueduct Perilymphatic aqueduct Ear

11 Enlarged canal and sac Normal Mondini malformation Pendred Syndrome Hearing loss, usually prelingual Goiter in 2nd decade, most are euthyroid Large vestibular aqueduct and endolymphatic sac Upper 2/3 of cochlea is poorly formed

in 2nd decade, most are euthyroid Large vestibular

12 Semicircular canal hypoplasia Normal CHARGE Syndrome Coloboma of the iris or retina Heart defects Atresia or stenosis of the choanae Retarded growth and development Genital hypoplasia in males Ear anomalies

defects Atresia or stenosis of the choanae Retarded

13 Neural crest cell migration in early embryonic development is critical to both hearing and pigmentation processes Waardenburg syndrome and LEOPARD syndrome both involve defects in pigmentation and hearing loss

pigmentation processes Waardenburg syndrome and

14 Accounts for 2-3% of all congenital deafness Several types of Waardenburg syndrome, most common type I Autosomal dominant inheritance PAX3 (2q35) and MITF (3p1) genes implicated in WS-I and WS-2

15 White forelock Heterochromia irides Synophrys Telecanthus Nl intelligence Nl lifespan

16 Autosomal dominant inheritance Gene same as gene for Neurofibromatosis type 1 (NF1)

17 Lentigenes EKG abnormalities Ocular hypertelorism Pulmonic stenosis Abnormal genitalia Retarded growth Deafness

18 Retinal abnormalities seen in approx. 10% of deaf population Most commonly Retinitis Pigmentosa (RP - progressive night blindness) Usher syndrome, Refsum disease are autosomal recessive disorders and Norrie disease is X-linked recessive Suggest that all deaf individuals have ophthalmologic evaluations

night blindness) Usher syndrome, Refsum disease are autosomal recessive

19 Progressive night blindness due to RP Sensorineural hearing loss Eventual blindness and deafness Balance problems Multiple different genes can cause

20 Renal problems occur in a significant number of individuals with deafness Primarily accounted for by 2 diseases: Alport syndrome and BOR syndrome Suggested that all children with hearing loss have evaluation of kidney structure and function

syndrome and BOR syndrome Suggested that all children with

21 Progressive hearing loss in teen age or early adult years Renal problems characterized by hematuria and proteinuria; sometimes leading to end-stage renal failure Inherited as X-linked dominant or autosomal recessive trait Gene testing available

22 Presence of prolonged QT and heart arhythmia is known as Long QT syndrome When associated with SNHL results in a condition called Jervell-Lange-Nielsen JLN is inherited as an autosomal recessive condition, but heterozygotes display long QT intervals Genetic testing for JLN is available clinically - genes involved are KVLQT1 and KCNE1

23 Goiter/thyroid dysfunction occurs in Pendred syndrome Most common genetic cause of deafness, accounting for 5% of deaf individuals PDS gene at 7q31 responsible for Pendred syndrome and some nonsyndromic hearing loss (DFNB4) Autosomal recessive inheritance

24 Hundreds of other genes which result in SNHL with other physical findings Some of these conditions are very rare, others common Identification of SNHL genes continues at a fast rate, but the utility of genetic testing for many of these conditions is not keeping pace

25 Aka Hemifacial Microsomia Features include: facial asymmetry eye abnormalities (epibulbar dermoid) ear malformations vertebral anomalies Sporadic inheritance

26 Features include: downslanting eyes eyelid colobomas dysplastic ears & conductive deafness small chin nl intelligence Autosomal dominant inheritance Gene testing available

27 History, Physical Exam & Audiology evaluation Diagnosis Apparent Diagnosis Unclear Treatment Bilateral Unilateral Sev - Prof Mod - Sev Mild - Mod CT Scan Serial Audiograms? C26 screening C26 screen +/+ +/- -/- C30 screen +/+ -/- Genetic + + Counseling CT scan EKG - CT scan + - Treatment C26 screen - - Lab tests as appropriate

28 Inherited in autosomal dominant, recessive, X-linked recessive and mitochondrial patterns DFN - X-linked (2-3%) DFNA - Autosomal dominant (10-20%) DFNB - Autosomal recessive (75-80%) Mitochondrial (< 1%)

29 Accounts for 10% of all hearing loss Accounts for 30% of all sporadic deafness Accounts for 50-80% of autosomal recessive hearing loss Gene codes a gap junction in the cochlea (GJB2) 1/50 US Caucasians carry a mutation

30 Hearing loss is prelingual Hearing loss is non-progressive Severity varies both between families and within a given family No health or learning problems associated Connexin 26 gene is implicated in KID syndrome (keratoderma, ichthyosis, deafness)

31 Gene codes a gap junction in the cochlea (GJB6) Mutations can interact with mutations in Connexin 26 to result in recessive hearing loss Accounts for 3% of all recessive hearing loss but is much more common in the Spanish population May account for deafness in 30-70% of Connexin 26 heterozygotes

32 Genetic testing is available for only a few of the genes which have currently been identified for NSHL At present, genetic counseling very often consists of risk appraisal without the option of DNA testing or prenatal diagnosis by DNA or other methods Advances in the field may result in rapid changes to what we are able to offer families

Objectives Role of Medical Genetics in Hearing Loss Evaluation. 5 y.o. boy with severe SNHL

Objectives Role of Medical Genetics in Hearing Loss Evaluation Millan Patel, MD UBC Dept. of Medical Genetics October 22, 2010 Case presentation to illustrate importance of defining syndromic hearing loss